Fig. 5.

R_CorrTissue% (ml × 100 g⁻¹) of [³H]corticosterone in the absence and presence of unlabeled cortisol in wild-type mice using in situ brain/choroid plexus perfusion technique. [³H]corticosterone (3.8 nm), along with [¹⁴C]sucrose (vascular space marker; 0.5–1.0 nm), was administered by a slow-drive syringe pump into the artificial plasma containing unlabeled cortisol (30 or 300 μm). After a perfusion time of 20 min, the mouse was decapitated, and selected brain regions (open white bar, frontal cortex; light gray bar, hippocampus; closed black bar, hypothalamus; dark gray bar, cerebellum) (A) and choroid plexus and pituitary gland (open white bar, choroid plexus; closed black bar, pituitary gland) (B) were sampled. The concentration of [³H] or [¹⁴C] radioactivity in the tissues (dpm g⁻¹) is expressed as a percentage of that in the artificial plasma (dpm ml⁻¹). The uptake of [³H]corticosterone in the hypothalamus and cerebellum was significantly decreased in the presence of 300 μm of unlabeled cortisol compared with wild-type controls (P = 0.017 and P = 0.002, respectively, one-way ANOVA, vascular space corrected), and the uptake of [³H]corticosterone in the choroid plexus and the pituitary gland was also significantly decreased in the presence of both concentrations of unlabeled cortisol compared with wild-type controls (both P < 0.001, one-way ANOVA, corrected for extracellular space) (n = 20–32). *, Significant difference (P < 0.05) when compared with controls.